Add missing expression help

resources/function_help/json/flip_coordinates

@@ -0,0 +1,8 @@
+{
+  "name": "flip_coordinates",
+  "type": "function",
+  "description": "Returns a copy of the geometry with the x and y coordinates swapped. Useful for repairing geometries which have had their latitude and longitude values reversed.",
+  "arguments": [ {"arg":"geom","description":"a geometry"}],
+  "examples": [ { "expression":"geom_to_wkt(flip_coordinates(make_point(1, 2)))", "returns":"Point (2 1)"}
+  ]
+}